Re-contention-based co-existence on a shared communication medium

ABSTRACT

Techniques for managing re-contention on a shared communication medium are disclosed. In order to facilitate re-contending for access to the communication medium, an access point may adjust one or more uplink transmission parameters associated with a triggering condition for invoking a contention timer. In addition or as an alternative, the access point may mute transmission on the communication medium during one or more symbol periods designated for transmission. In addition or as an alternative, the access point may configure a timing advance to create a re-contention gap.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 62/207,319, entitled “Re-Contention-Based Co-Existenceon a Shared Communication Medium,” filed Aug. 19, 2015, assigned to theassignee hereof, and expressly incorporated herein by reference in itsentirety.

The present application is also related to the following co-pending U.S.Patent Application(s): “Re-Contention-Based Co-Existence on a SharedCommunication Medium,” having U.S. application Ser. No. 15/240,584,filed Aug. 18, 2016, and “Re-Contention-Based Co-Existence on a SharedCommunication Medium,” having U.S. application Ser. No. 15/240,678,filed Aug. 18, 2016, each assigned to the assignee hereof, and eachexpressly incorporated herein by reference in its entirety

INTRODUCTION

Aspects of this disclosure relate generally to telecommunications, andmore particularly to operations on a shared communication medium and thelike.

Wireless communication systems are widely deployed to provide varioustypes of communication content, such as voice, data, multimedia, and soon. Typical wireless communication systems are multiple-access systemscapable of supporting communication with multiple users by sharingavailable system resources (e.g., bandwidth, transmit power, etc.).Examples of such multiple-access systems include Code Division MultipleAccess (CDMA) systems, Time Division Multiple Access (TDMA) systems,Frequency Division Multiple Access (FDMA) systems, Orthogonal FrequencyDivision Multiple Access (OFDMA) systems, and others. These systems areoften deployed in conformity with specifications such as Long TermEvolution (LTE) provided by the Third Generation Partnership Project(3GPP), Ultra Mobile Broadband (UMB) and Evolution Data Optimized(EV-DO) provided by the Third Generation Partnership Project 2 (3GPP2),802.11 provided by the Institute of Electrical and Electronics Engineers(IEEE), etc.

In cellular networks, “macro cell” access points provide connectivityand coverage to a large number of users over a certain geographicalarea. A macro network deployment is carefully planned, designed, andimplemented to offer good coverage over the geographical region. Toimprove indoor or other specific geographic coverage, such as forresidential homes and office buildings, additional “small cell,”typically low-power access points have recently begun to be deployed tosupplement conventional macro networks. Small cell access points mayalso provide incremental capacity growth, richer user experience, and soon.

Small cell LTE operations, for example, have been extended into theunlicensed frequency spectrum such as the Unlicensed NationalInformation Infrastructure (U-NII) band used by Wireless Local AreaNetwork (WLAN) technologies. This extension of small cell LTE operationis designed to increase spectral efficiency and hence capacity of theLTE system. However, it may also encroach on the operations of otherRadio Access Technologies (RATs) that typically utilize the sameunlicensed bands, most notably IEEE 802.11x WLAN technologies generallyreferred to as “Wi-Fi.”

SUMMARY

The following summary is an overview provided solely to aid in thedescription of various aspects of the disclosure and is provided solelyfor illustration of the aspects and not limitation thereof.

In one example, a communication method is disclosed. The method mayinclude, for example, contending for access to a communication mediumfor a series of subframes associated with a Time Division Duplexing(TDD) frame structure; transmitting on the communication medium during afirst portion of the series of subframes; refraining from transmittingon the communication medium during a second portion of the series ofsubframes; adjusting one or more uplink transmission parametersassociated with a triggering condition for invoking a contention timer;re-contending for access to the communication medium for a third portionof the series of subframes based on the contention timer; andtransmitting on the communication medium during the third portion of theseries of subframes.

In another example, a communication apparatus is disclosed. Theapparatus may include, for example, at least one transceiver, at leastone processor, and at least one memory coupled to the at least oneprocessor. The at least one processor and the at least one memory may beconfigured to contend for access to a communication medium for a seriesof subframes associated with a TDD frame structure. The at least onetransceiver may be configured to transmit on the communication mediumduring a first portion of the series of subframes and to refrain fromtransmitting on the communication medium during a second portion of theseries of subframes. The at least one processor and the at least onememory may be further configured to adjust one or more uplinktransmission parameters associated with a triggering condition forinvoking a contention timer and to re-contend for access to thecommunication medium for a third portion of the series of subframesbased on the contention timer. The at least one transceiver may befurther configured to transmit on the communication medium during thethird portion of the series of subframes.

In another example, another communication apparatus is disclosed. Theapparatus may include, for example, means for contending for access to acommunication medium for a series of subframes associated with a TDDframe structure; means for transmitting on the communication mediumduring a first portion of the series of subframes; means for refrainingfrom transmitting on the communication medium during a second portion ofthe series of subframes; means for adjusting one or more uplinktransmission parameters associated with a triggering condition forinvoking a contention timer; means for re-contending for access to thecommunication medium for a third portion of the series of subframesbased on the contention timer; and means for transmitting on thecommunication medium during the third portion of the series ofsubframes.

In another example, a transitory or non-transitory computer-readablemedium is disclosed. The computer-readable medium may include, forexample, code for contending for access to a communication medium for aseries of subframes associated with a TDD frame structure; code fortransmitting on the communication medium during a first portion of theseries of subframes; code for refraining from transmitting on thecommunication medium during a second portion of the series of subframes;code for adjusting one or more uplink transmission parameters associatedwith a triggering condition for invoking a contention timer; code forre-contending for access to the communication medium for a third portionof the series of subframes based on the contention timer; and code fortransmitting on the communication medium during the third portion of theseries of subframes.

In another example, another communication method is disclosed. Themethod may include, for example, contending for access to acommunication medium for a series of subframes associated with a TDDframe structure; transmitting on the communication medium during a firstportion of the series of subframes; refraining from transmitting on thecommunication medium during a second portion of the series of subframes;muting transmission on the communication medium during one or moresymbol periods designated for transmission during the series ofsubframes; re-contending, during the one or more symbol periods, foraccess to the communication medium for a third portion of the series ofsubframes; and transmitting on the communication medium during the thirdportion of the series of subframes.

In another example, a communication apparatus is disclosed. Theapparatus may include, for example, at least one transceiver, at leastone processor, and at least one memory coupled to the at least oneprocessor. The at least one processor and the at least one memory may beconfigured to contend for access to a communication medium for a seriesof subframes associated with a TDD frame structure. The at least onetransceiver may be configured to transmit on the communication mediumduring a first portion of the series of subframes and to refrain fromtransmitting on the communication medium during a second portion of theseries of subframes. The at least one processor and the at least onememory may be further configured to mute transmission on thecommunication medium during one or more symbol periods designated fortransmission during the series of subframes and to re-contend, duringthe one or more symbol periods, for access to the communication mediumfor a third portion of the series of subframes. The at least onetransceiver may be further configured to transmit on the communicationmedium during the third portion of the series of subframes.

In another example, another communication apparatus is disclosed. Theapparatus may include, for example, means for contending for access to acommunication medium for a series of subframes associated with a TDDframe structure; means for transmitting on the communication mediumduring a first portion of the series of subframes; means for refrainingfrom transmitting on the communication medium during a second portion ofthe series of subframes; means for muting transmission on thecommunication medium during one or more symbol periods designated fortransmission during the series of subframes; means for re-contending,during the one or more symbol periods, for access to the communicationmedium for a third portion of the series of subframes; and means fortransmitting on the communication medium during the third portion of theseries of subframes.

In another example, another transitory or non-transitorycomputer-readable medium is disclosed. The computer-readable medium mayinclude, for example, code for contending for access to a communicationmedium for a series of subframes associated with a TDD frame structure;code for transmitting on the communication medium during a first portionof the series of subframes; code for refraining from transmitting on thecommunication medium during a second portion of the series of subframes;code for muting transmission on the communication medium during one ormore symbol periods designated for transmission during the series ofsubframes; code for re-contending, during the one or more symbolperiods, for access to the communication medium for a third portion ofthe series of subframes; and code for transmitting on the communicationmedium during the third portion of the series of subframes.

In another example, another communication method is disclosed. Themethod may include, for example, contending for access to acommunication medium for a series of subframes associated with a TDDframe structure; transmitting on the communication medium during a firstportion of the series of subframes; refraining from transmitting on thecommunication medium during a second portion of the series of subframes;configuring a timing advance of the second portion of the series ofsubframes to create a re-contention gap between the second portion ofthe series of subframes and a third portion of the series of subframes;re-contending, during the re-contention gap, for access to thecommunication medium for the third portion of the series of subframes;and transmitting on the communication medium during the third portion ofthe series of subframes.

In another example, another communication apparatus is disclosed. Theapparatus may include, for example, at least one transceiver, at leastone processor, and at least one memory coupled to the at least oneprocessor. The at least one processor and the at least one memory may beconfigured to contend for access to a communication medium for a seriesof subframes associated with a TDD frame structure. The at least onetransceiver may be configured to transmit on the communication mediumduring a first portion of the series of subframes and to refrain fromtransmitting on the communication medium during a second portion of theseries of subframes. The at least one processor and the at least onememory may be further configured to configure a timing advance of thesecond portion of the series of subframes to create a re-contention gapbetween the second portion of the series of subframes and a thirdportion of the series of subframes and re-contend, during there-contention gap, for access to the communication medium for the thirdportion of the series of subframes. The at least one transceiver may befurther configured to transmit on the communication medium during thethird portion of the series of subframes.

In another example, another communication apparatus is disclosed. Theapparatus may include, for example, means for contending for access to acommunication medium for a series of subframes associated with a TDDframe structure; means for transmitting on the communication mediumduring a first portion of the series of subframes; means for refrainingfrom transmitting on the communication medium during a second portion ofthe series of subframes; means for configuring a timing advance of thesecond portion of the series of subframes to create a re-contention gapbetween the second portion of the series of subframes and a thirdportion of the series of subframes; means for re-contending, during there-contention gap, for access to the communication medium for the thirdportion of the series of subframes; and means for transmitting on thecommunication medium during the third portion of the series ofsubframes.

In another example, another transitory or non-transitorycomputer-readable medium is disclosed. The computer-readable medium mayinclude, for example, code for contending for access to a communicationmedium for a series of subframes associated with a TDD frame structure;code for transmitting on the communication medium during a first portionof the series of subframes; code for refraining from transmitting on thecommunication medium during a second portion of the series of subframes;code for configuring a timing advance of the second portion of theseries of subframes to create a re-contention gap between the secondportion of the series of subframes and a third portion of the series ofsubframes; code for re-contending, during the re-contention gap, foraccess to the communication medium for the third portion of the seriesof subframes; and code for transmitting on the communication mediumduring the third portion of the series of subframes.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof.

FIG. 1 is a system-level diagram illustrating an example wirelessnetwork environment.

FIG. 2 illustrates an example virtual Time Division Duplexing (TDD)frame structure.

FIG. 3 is a system-level diagram illustrating an uplink transmissioncontrol scheme for facilitating communication medium re-contention.

FIG. 4 illustrates an example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2.

FIG. 5 illustrates another example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2.

FIG. 6 illustrates another example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2.

FIG. 7 is a resource map diagram illustrating an example physicalchannel muting scheme for facilitating communication mediumre-contention.

FIG. 8 illustrates an example of physical channel muting in the uplinkdirection in accordance with the TDD frame structure of FIG. 2.

FIG. 9 illustrates an example of physical channel muting in the downlinkdirection in accordance with the TDD frame structure of FIG. 2.

FIG. 10 illustrates an example of a timing advance scheme forfacilitating communication medium re-contention.

FIG. 11 illustrates another example of a timing advance scheme forfacilitating communication medium re-contention.

FIG. 12 is a flow diagram illustrating an example method ofcommunication in accordance with the techniques described herein.

FIG. 13 is a flow diagram illustrating another example method ofcommunication in accordance with the techniques described herein.

FIG. 14 is a flow diagram illustrating another example method ofcommunication in accordance with the techniques described herein.

FIG. 15 is a device-level diagram illustrating example components of anaccess point and an access terminal in more detail.

FIG. 16 illustrates an example apparatus represented as a series ofinterrelated functional modules.

FIG. 17 illustrates an example apparatus represented as a series ofinterrelated functional modules.

FIG. 18 illustrates an example apparatus represented as a series ofinterrelated functional modules.

DETAILED DESCRIPTION

The present disclosure relates generally to co-existence techniquesbetween Radio Access Technologies (RATs) operating on a sharedcommunication medium subject to contention. For deployments in whichcontiguous occupation of the communication medium is required,re-contention may be performed to re-access the communication medium fora period of downlink subframes following a period of uplink subframes.In some designs, re-contention may be facilitated by an uplinktransmission control scheme in which uplink transmission parametersdictating, for example, transmission power, multi-user scheduling, orsub-band scheduling, may be adjusted to prevent or at least reduce thelikelihood that uplink transmission will trigger a contention timer. Inaddition or as an alternative, transmission may be scheduled during oneor more symbol periods of an uplink or downlink subframe whilerefraining from configuring transmission during those symbol periods inorder to provide an opportunity for re-contention. In addition or as analternative, a timing advance may be configured for the period of uplinksubframes to create a re-contention gap prior to the period of downlinksubframes in order to provide another opportunity for re-contention.

More specific aspects of the disclosure are provided in the followingdescription and related drawings directed to various examples providedfor illustration purposes. Alternate aspects may be devised withoutdeparting from the scope of the disclosure. Additionally, well-knownaspects of the disclosure may not be described in detail or may beomitted so as not to obscure more relevant details.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., Application Specific Integrated Circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. In addition, for each of theaspects described herein, the corresponding form of any such aspect maybe implemented as, for example, “logic configured to” perform thedescribed action.

FIG. 1 is a system-level diagram illustrating an example wirelessnetwork environment, shown by way of example as including a “primary”Radio Access Technology (RAT) system 100 and a “competing” RAT system150. Each system may be composed of different wireless nodes generallycapable of receiving and/or transmitting over a wireless link, includinginformation related to various types of communication (e.g., voice,data, multimedia services, associated control signaling, etc.). Theprimary RAT system 100 is shown as including an access point 110 and anaccess terminal 120 in communication with each other over a wirelesslink 130. The competing RAT system 150 is shown as including twocompeting nodes 152 in communication with each other over a separatewireless link 132, and may similarly include one or more access points,access terminals, or other types of wireless nodes. As an example, theaccess point 110 and the access terminal 120 of the primary RAT system100 may communicate via the wireless link 130 in accordance with LongTerm Evolution (LTE) technology, while the competing nodes 152 of thecompeting RAT system 150 may communicate via the wireless link 132 inaccordance with Wi-Fi technology. It will be appreciated that eachsystem may support any number of wireless nodes distributed throughout ageographic region, with the illustrated entities being shown forillustration purposes only.

Unless otherwise noted, the terms “access terminal” and “access point”are not intended to be specific or limited to any particular RAT. Ingeneral, access terminals may be any wireless communication deviceallowing a user to communicate over a communications network (e.g., amobile phone, router, personal computer, server, entertainment device,Internet of Things (TOT)/Internet of Everything (ME) capable device,in-vehicle communication device, etc.), and may be alternativelyreferred to in different RAT environments as a User Device (UD), aMobile Station (MS), a Subscriber Station (STA), a User Equipment (UE),etc. Similarly, an access point may operate according to one or severalRATs in communicating with access terminals depending on the network inwhich the access point is deployed, and may be alternatively referred toas a Base Station (BS), a Network Node, a NodeB, an evolved NodeB (eNB),etc. Such an access point may correspond to a small cell access point,for example. “Small cells” generally refer to a class of low-poweredaccess points that may include or be otherwise referred to as femtocells, pico cells, micro cells, Wireless Local Area Network (WLAN)access points, other small coverage area access points, etc. Small cellsmay be deployed to supplement macro cell coverage, which may cover a fewblocks within a neighborhood or several square miles in a ruralenvironment, thereby leading to improved signaling, incremental capacitygrowth, richer user experience, and so on.

Returning to FIG. 1, the wireless link 130 used by the primary RATsystem 100 and the wireless link 132 used by the competing RAT system150 may operate over a shared communication medium 140. A communicationmedium of this type may be composed of one or more frequency, time,and/or space communication resources (e.g., encompassing one or morechannels across one or more carriers). As an example, the communicationmedium 140 may correspond to at least a portion of an unlicensedfrequency band. Although different licensed frequency bands have beenreserved for certain communications (e.g., by a government entity suchas the Federal Communications Commission (FCC) in the United States),some systems, in particular those employing small cell access points,have extended operation into unlicensed frequency bands such as theUnlicensed National Information Infrastructure (U-NII) band used by WLANtechnologies including Wi-Fi.

Due to the shared use of the communication medium 140, there is thepotential for cross-link interference between the wireless link 130 andthe wireless link 132. Further, some RATs and some jurisdictions mayrequire contention or “Listen Before Talk (LBT)” for access to thecommunication medium 140. As an example, a Clear Channel Assessment(CCA) protocol may be used in which each device verifies via mediumsensing the absence of other traffic on a shared communication mediumbefore seizing (and in some cases reserving) the communication mediumfor its own transmissions. In some designs, the CCA protocol may includedistinct CCA Preamble Detection (CCA-PD) and CCA Energy Detection(CCA-ED) mechanisms for yielding the communication medium to intra-RATand inter-RAT traffic, respectively. The European TelecommunicationsStandards Institute (ETSI), for example, mandates contention for alldevices regardless of their RAT on certain communication media such asunlicensed frequency bands.

As will be described in more detail below, the access point 110 and/orthe access terminal 120 may be variously configured in accordance withthe teachings herein to provide or otherwise support the contention andre-contention techniques discussed briefly above. For example, theaccess point 110 may include a medium access manager 112 and the accessterminal 120 may include a medium access manager 122. The medium accessmanager 112 and/or the medium access manager 122 may be configured indifferent ways to manage contending for access to the communicationmedium 140.

FIG. 2 illustrates an example virtual Time Division Duplexing (TDD)frame structure that may be implemented for the primary RAT system 100on the communication medium 140 to facilitate contention-based accessbetween the access point 110/access terminal 120 and the competing RATsystem 150.

The illustrated frame structure includes a series of radio frames (RFs)that are numbered in accordance with a System Frame Number (SFN)numerology (SFN N, N+1, N+2, etc.) and divided into respective subframes(SFs), which may also be numbered for reference (e.g., SF0, SF1, etc.).As an example, the LTE frame structure includes system frames that aredivided into 1024 numbered radio frames composed of 10 subframes each,which together constitute an SFN cycle (e.g., lasting 10.24 s for 10 msradio frames having 1 ms subframes). The use of a frame structure mayprovide more natural and efficient coordination among devices than moread hoc signaling techniques.

The example frame structure of FIG. 2 is TDD in that each subframe maybe variously operated at different times as a downlink (D), uplink (U),or special (S) subframe. In general, downlink subframes are reserved fortransmitting downlink information from the access point 110 to theaccess terminal 120, uplink subframes are reserved for transmittinguplink information from the access terminal 120 to the access point 110,and special subframes may include a downlink portion and an uplinkportion separated by a guard period. Different arrangements of downlink,uplink, and special subframes within a radio frame may be referred to asdifferent TDD configurations. Returning to the LTE example above, theTDD variant of the LTE frame structure includes 7 TDD configurations(TDD Config 0 through TDD Config 6), with each configuration having adifferent arrangement of downlink, uplink, and special subframes. Forexample, some TDD configurations may have more downlink subframes andsome may have more uplink subframes to accommodate different trafficscenarios. In the illustrated example of FIG. 2, a TDD configuration isemployed that is similar to TDD Config 3 in LTE. The particular TDDconfiguration employed may be broadcast by the access point 110 using aSystem Information Block (SIB) message, a new physical channel toindicate the TDD frame format in the control region, or the like (e.g.,a SIB-1 message in LTE).

Although each TDD configuration is different, there may be one or moresubframes that are the same across all TDD configurations. Thesesubframes are referred to herein as anchor subframes. Returning again tothe LTE example above, the subframe SF0 is a downlink subframe, SF1 is aspecial subframe, SF2 is an uplink subframe, and SF5 is a downlinksubframe in each radio frame across each of the TDD configurations TDDConfig 0 through TDD Config 6. In the illustrated example, the anchorsubframes similarly correspond to the subframes SF0, SF1, SF2, and SF5of each radio frame, although it will be appreciated that the specificanchor carrier designations may vary across different systems.

The example frame structure of FIG. 2 is virtual in that each subframemay or may not be occupied by primary RAT signaling in any giveninstance due to the contention procedure for accessing the communicationmedium 140. In general, if the access point 110 or the access terminal120 fails to win contention for a given subframe that subframe may besilenced.

At some point during the contention process, the communication medium140 becomes clear (e.g., CCA Clear) and the access point 110, forexample, seizes it. In order to reserve the communication medium 140 foritself for a Transmission Opportunity (TXOP) having a certain duration(e.g., one radio frame), the access point 110 may send a channelreservation message (RSV) 202 defined for the competing RAT system 150.The channel reservation message 202 may be transmitted over thecommunication medium 140 (e.g., via a competing-RAT-specific transceiveralso belonging to the access point 110) to reserve the communicationmedium 140 for primary RAT operation. Example channel reservationmessages may include, for example, 802.11a Data packets,Clear-to-Send-to-Self (CTS2S) messages, Request-to-Send (RTS) messages,Clear-to-Send (CTS) messages, Physical Layer Convergence Protocol (PLCP)headers (e.g., a legacy signal (L-SIG), a high throughput signal(HT-SIG), or very high throughput signal (VHT-SIG)), and the like for acompeting Wi-Fi RAT, or other similar messages defined for othercompeting RATs of interest. The channel reservation message 202 mayinclude a duration indication (e.g., a Network Allocation Vector (NAV))corresponding to the duration of the target TXOP for which the accesspoint 110 contended for access.

In some designs, the channel reservation message 202 may be sent as aone-way communication not invoking any acknowledgement (e.g., CTS2S). Inother designs, the channel reservation message 202 may be sent as atwo-way handshake communication that is acknowledged by each receivingentity (e.g., CTS/RTS). In addition, the channel reservation message 202may be sent as a deep handshake signal with a larger coverage area toreach additional, otherwise hidden nodes that may be impacted by primaryRAT communication but not able to receive short-range channelreservation messages (e.g., eCTS/eRTS).

In some deployments, reservation of a given TXOP by the access point 110may be sufficient to satisfy the contention requirements for alldownlink and uplink transmissions that are scheduled during the TXOP. Inother deployments, however, contiguous occupation of the communicationmedium 140 may be required. One or more uplink subframes situatedbetween downlink or special subframes may create a transmission gap thatdisrupts the required continuity. As shown in FIG. 2, for example, whilethe access point 110 may transmit over the communication medium 140during a first period 212 (including the first downlink subframe andspecial subframe of the TXOP) and a third period 216 (including the lastfive downlink subframes), the access point 110 may not transmit duringan intervening second period 214 (including the middle three uplinksubframes) which is designated for transmission by the access terminal120. Thus, in some deployments, the access point 110 may be required tore-contend for access to the communication medium 140 for any downlinksubframes that follow one or more uplink subframes, such as at theuplink-to-downlink transition boundary 218 between the second period 214and the third period 216.

In some designs, the access point 110 may simply re-contend for accessto the communication medium 140 in the next downlink subframe (e.g., thefirst downlink subframe following the uplink-to-downlink transitionboundary 218). However, this may result in a loss of efficiency becausethe downlink subframe in which re-contention is performed may beunavailable for other signaling, particularly for RATs in which there isno partial subframe support. In other designs, the access point 110 mayminimize the number of re-contention instances by selecting a TDDconfiguration that includes a relatively small number ofuplink-to-downlink transitions. In LTE, for example, TDD Config 3includes only one such transition within each radio frame. However, TDDConfig 3 provides only a 30% duty cycle for uplink traffic, which may beinsufficient for some scenarios.

A more flexible TDD configuration may also be employed in which anadaptable number of uplink subframes is provided in sequence at the endof a radio frame, thereby eliminating uplink-to-downlink transitionswithin the radio frame altogether. Even so, such a configuration stillrequires an uplink-to-downlink transition between radio frames, which,for any TXOP spanning more than one radio frame, may necessitatere-contention during—and therefore impede utilization of—the last uplinksubframe of the radio frame or the first downlink subframe of the nextradio frame.

FIG. 3 is a system-level diagram illustrating an uplink transmissioncontrol scheme for facilitating communication medium re-contention. Inthis example, the access point 110 is shown as communicating with theaccess terminal 120 over the communication medium 140 in an innercoverage region 302 where the corresponding wireless link 130 isrelatively strong. By contrast, the access point 110 may also serveother access terminals that are located in an outer coverage region 304with wireless links that are by comparison relatively weak (shown by wayof example as the optional access terminal 320 with a correspondingwireless link 330).

Because the wireless link 130 between the access point 110 and theaccess terminal 120 is relatively strong, signaling sent from the accessterminal 120 to the access point 110 during an uplink subframe (e.g.,the last uplink subframe preceding the uplink-to-downlink transitionboundary 218) may make it more difficult for the access point 110 tore-contend for access to the communication medium 140. In particular,signaling energy received at the access point 110 above a backoffthreshold (e.g., −60 dBm) may trigger the invocation of a contentiontimer 310 that dictates a backoff period for which the access point 110must wait before contending again. This backoff period may extend intoor beyond the next downlink subframe (e.g., the first downlink subframefollowing the uplink-to-downlink transition boundary 218) and preventthe access point 110 from utilizing this subframe even though thissubframe has already been reserved and even though the signaling deemedto be conflicting is actually from the access terminal 120 rather than,for example, the competing RAT system 150.

To better facilitate re-contention under such a scenario, in somedesigns, the access point 110 may adjust one or more uplink transmissionparameters 312 associated with a triggering condition for invoking(starting/restarting) the contention timer 310. The transmissionparameters 312 may be adjusted to prevent or at least reduce thelikelihood that the contention timer 310 is triggered by signaling fromthe access terminal 120, in particular in anticipation of anuplink-to-downlink transition (e.g., during the last uplink subframepreceding the uplink-to-downlink transition boundary 218). Thetriggering condition may correspond, for example, to a backoff threshold(e.g., a threshold signal strength for a threshold duration). Thetransmission parameters 312 may be adjusted in response to the proximityof the access terminal 120 to the access point 110.

FIG. 4 illustrates an example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2. It willbe appreciated that adjustments to the uplink transmission parameters312 may be conveyed to the access terminal 120 in different ways,including as part of different direct or broadcast messaging schemes aswell as at different times. The particular timing and message formatshown in FIG. 4 is provided for illustrations purposes only.

In this example, the transmission parameters 312 may include atransmission power parameter 402. The transmission power parameter 402may be adjusted to limit the signal strength or the number oftransmission resources (e.g., number of resource blocks) afforded to theaccess terminal 120 such that the signaling energy of the accessterminal 120 as perceived by the access point 110 is not high enough tomeet the triggering condition for invoking the contention timer 310.While a reduction in transmission power may provide poorer performancewith higher relative interference for the access terminal 120, becauseof its proximity to the access point 110 this level of performance maystill be satisfactory while allowing the access point 110 to immediatelyre-contend for access to the communication medium 140. Meanwhile,returning to the example of FIG. 3, the distance of the other accessterminal 320 operating in the outer coverage region 304 makes itunlikely that the signaling energy of the access terminal 320 asperceived by the access point 110 will be high enough to meet thetriggering condition for invoking the contention timer 310. The priorreservation makes it also unlikely that interference from other sourcessuch as the competing RAT system 150 will impede the re-contentionprocess.

FIG. 5 illustrates another example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2. It willagain be appreciated that adjustments to the uplink transmissionparameters 312 may be conveyed to the access terminal 120 in differentways, including as part of different direct or broadcast messagingschemes as well as at different times. The particular timing and messageformat shown in FIG. 5 is provided for illustrations purposes only.

In this example, the uplink transmission parameters 312 may include amulti-user scheduling parameter 502. The multi-user scheduling parameter502 may be adjusted to schedule the access terminal 120 only in earlieruplink subframes (e.g., the second-to-last uplink subframe preceding theuplink-to-downlink transition boundary 218) where the contention timer310 is not problematic. Meanwhile, returning again to the example ofFIG. 3, the other access terminal 320 operating in the outer coverageregion 304 may be more safely scheduled closer to an uplink-to-downlinktransition (e.g., during the last uplink subframe preceding theuplink-to-downlink transition boundary 218). While this approach toscheduling may diminish certain benefits related to scheduling timediversity, each access terminal may still be scheduled fairly and thedistance of the other access terminal 320 operating in the outercoverage region 304 makes it is unlikely that it will meet thetriggering condition for invoking the contention timer 310.

FIG. 6 illustrates another example of uplink transmission parameteradjustment in accordance with the TDD frame structure of FIG. 2. It willagain be appreciated that adjustments to the uplink transmissionparameters 312 may be conveyed to the access terminal 120 in differentways, including as part of different direct or broadcast messagingschemes as well as at different times. The particular timing and messageformat shown in FIG. 6 is provided for illustrations purposes only.

In this example, the transmission parameters 312 may include a sub-bandscheduling parameter 602. In a scenario in which it is impractical forthe access point 110 to schedule the access terminal 120 around anuplink-to-downlink transition (e.g., when there are no other accessterminals like the access terminal 320), the sub-band schedulingparameter may be adjusted to schedule the access terminal 120 only in asubset of resources spanning the reserved bandwidth (e.g., every otherresource block) and the access point 110 may monitor signaling energy ina complementary set of resources (e.g., the unscheduled set of resourceblocks). While the monitored signaling energy may still conform tocontention requirements by consisting of a wideband measurement in thesense that the complementary set of resources span a wideband range, itis unlikely that it will meet the triggering condition for invoking thecontention timer 310.

FIG. 7 is a resource map diagram illustrating an example physicalchannel muting scheme for facilitating communication mediumre-contention. As shown, one or more symbols at a given symbolperiod/subcarrier location may be muted in either uplink subframes,downlink subframes, or a combination thereof. In the illustratedexample, one symbol period is shown as being muted but it will beappreciated that more than one symbol period may be muted as appropriatefor a particular contention scheme. Further, each subcarrier in a givensymbol period is shown as being muted but it will be appreciated thatonly a subset of symbols may instead be muted in each symbol period asappropriate to map to a given channel.

By designating for transmission (e.g., via scheduling or otherwiseconfiguring) one or more of the last symbol periods during an uplinksubframe (e.g., the last uplink subframe preceding theuplink-to-downlink transition boundary 218) or one or more of the firstsymbol periods during a downlink subframe (e.g., the first downlinksubframe following the uplink-to-downlink transition boundary 218) andthen muting transmission during these symbol periods, the access point110 may in effect reserve these symbol periods for re-contention. Thismay be done without compromising the entire subframe.

FIG. 8 illustrates an example of physical channel muting in the uplinkdirection in accordance with the TDD frame structure of FIG. 2. Asshown, resources during the last symbol period(s) of the uplink subframepreceding the uplink-to-downlink transition boundary 218 may bedesignated for reference signaling, for example, but not configured forany access terminal including the access terminal 120.

In the illustrated example, the access point 110 may advertise aSounding Reference Signal (SRS) gap, for example, during the last uplinksubframe preceding the uplink-to-downlink transition boundary 218 andthen refrain from configuring the access terminal 120 or any otheraccess terminal for SRS transmission during this time. Ordinarily, SRSsignaling is designated for a set of symbols of the last symbol periodof an uplink subframe and used to help facilitate wideband uplinkchannel estimation for use in uplink power control, link adaptation,sub-band scheduling (e.g., frequency-dependent uplink scheduling), andso on. The access terminal 120 may be configured to understand that anysymbol period designated for SRS signaling may not be used for othertransmissions. In this way, some channels such as a Physical UplinkControl Channel (PUCCH) may be completely silenced and other channelssuch as a Physical Uplink Shared Channel (PUSCH) may be partiallysilenced (referred to herein as puncturing) during this time to providean opportunity for re-contention.

FIG. 9 illustrates an example of physical channel muting in the downlinkdirection in accordance with the TDD frame structure of FIG. 2. Asshown, resources during the first symbol period(s) of the downlinksubframe following the uplink-to-downlink transition boundary 218 may beconfigured for control signaling, for example, but the control signalingmay be omitted.

In the illustrated example, the access point 110 may mute an ordinarilyconfigured Physical Downlink Control Channel (PDCCH) during the firstdownlink subframe (or the first few downlink subframes) following theuplink-to-downlink transition boundary 218 by refraining from sendingany actual PDCCH transmissions during this time. Instead, the accesspoint 110 may send the requisite control signaling via another channel(e.g., using Enhanced PDCCH (ePDCCH) over a Physical Downlink SharedChannel (PDSCH)) or rely on cross-carrier scheduling (e.g., via acorresponding Primary Cell (PCell) for PDCCH associated with a SecondaryCell (SCell)). Although there may be a loss of efficiency as well aslegacy support for some access terminals, this time may be used toprovide another opportunity for re-contention.

FIG. 10 illustrates an example of a timing advance scheme forfacilitating communication medium re-contention. In this example, atiming advance mechanism is used in conjunction with the virtual TDDframe structure of FIG. 2.

As shown, in order to provide a re-contention gap 1002, the timing ofthe uplink subframes in a reserved TXOP may be advanced such that eachuplink subframe commences earlier than normally scheduled. This may beachieved by sending a timing advance command 1004 to the access terminal120. The re-contention gap 1002 may be used by the access point 110 tore-contend for access to the communication medium 140.

FIG. 11 illustrates another example of a timing advance scheme forfacilitating communication medium re-contention. This example is similarto that of FIG. 10, except that the timing advance command 1004 furtherinstructs the access terminal 120 to shorten a preceding subframe (shownby way of example as the shortened special subframe 1106) and commencethe next uplink subframe early.

As an example, the timing advance may pull the uplink subframes into theshortened special subframe 1106 by a few (e.g., 1-3) symbol periods andthereby provide a re-contention gap 1002 on the order of a few hundredmicroseconds (e.g., 140 microseconds for a timing advance of 2 symbolperiods having a duration of 70 microseconds each).

Returning to FIG. 10, in some designs, the access point 110 may send an(optional) supplemental channel reservation message 1008, as shown, uponre-seizing the communication medium 140 as an additional protection. Theprior reservation makes it unlikely that interference from other sourcessuch as the competing RAT system 150 will impede the re-contentionprocess.

FIG. 12 is a flow diagram illustrating an example method ofcommunication in accordance with the techniques described above. Themethod 1200 may be performed, for example, by an access point (e.g., theaccess point 110 illustrated in FIG. 1) operating on a sharedcommunication medium. As an example, the communication medium mayinclude one or more time, frequency, or space resources on an unlicensedradio frequency band shared between LTE technology and Wi-Fi technologydevices.

As shown, the access point may contend for access to a communicationmedium for a series of subframes associated with a TDD frame structure(block 1202). The access point may then transmit on the communicationmedium during a first portion of the series of subframes (block 1204).The access point may, however, refrain from transmitting on thecommunication medium during a second portion of the series of subframes(block 1206).

At some point, the access point may adjust one or more uplinktransmission parameters associated with a triggering condition forinvoking a contention timer (block 1208). It will be appreciated thatthis operation may be performed at various times in relation to theother operations illustrated in FIG. 12, and that the listing ofoperations in FIG. 12 is not meant to convey a required or preferredordering.

The access point may subsequently re-contend for access to thecommunication medium for a third portion of the series of subframesbased on the contention timer (block 1210) and transmit on thecommunication medium during the third portion of the series of subframes(block 1212).

As discussed in more detail above, the triggering condition may include,for example, a backoff threshold. The adjusting (block 1208) may includetransmitting the one or more uplink transmission parameters to an accessterminal and may also be performed in response to a proximity of theaccess terminal to the access point.

In some designs, the one or more uplink transmission parameters mayinclude a transmission power parameter, with the adjusting (block 1208)including limiting a signal strength or a number of transmissionresources associated with an access terminal to below a level associatedwith the triggering condition. In addition or as an alternative, the oneor more uplink transmission parameters may include a multi-userscheduling parameter, with the adjusting (block 1208) includingrefraining from scheduling any access terminals having a signal strengthabove a threshold in a subframe that is adjacent to the third portion ofthe series of subframes. In addition or as an alternative, the one ormore uplink transmission parameters may include a sub-band schedulingparameter, with the adjusting (block 1208) including scheduling anaccess terminal in a first subset of resources of the second portion ofthe series of subframes and the re-contending (block 1210) includingmonitoring signaling on a second subset of resources of the secondportion of the series of subframes different from the first subset ofresources.

As also discussed above, a channel reservation message may betransmitted to reserve the communication medium for the series ofsubframes.

FIG. 13 is a flow diagram illustrating another example method ofcommunication in accordance with the techniques described above. Themethod 1300 may be performed, for example, by an access point (e.g., theaccess point 110 illustrated in FIG. 1) operating on a sharedcommunication medium. As an example, the communication medium mayinclude one or more time, frequency, or space resources on an unlicensedradio frequency band shared between LTE technology and Wi-Fi technologydevices.

As shown, the access point may contend for access to a communicationmedium for a series of subframes associated with a TDD frame structure(block 1302). The access point may then transmit on the communicationmedium during a first portion of the series of subframes (block 1304).The access point may, however, refrain from transmitting on thecommunication medium during a second portion of the series of subframes(block 1306).

At some point, the access point may mute transmission on thecommunication medium during one or more symbol periods designated fortransmission during the series of subframes (block 1308). It will beappreciated that this operation may be performed at various times inrelation to the other operations illustrated in FIG. 13, and that thelisting of operations in FIG. 13 is not meant to convey a required orpreferred ordering.

The access point may subsequently re-contend, during the one or moresymbol periods, for access to the communication medium for a thirdportion of the series of subframes (block 1310). The access point maythen transmit on the communication medium during the third portion ofthe series of subframes (block 1312).

As discussed in more detail above, the one or more symbol periods mayinclude, for example, a last symbol period of a last uplink subframe inthe second portion of the series of subframes, with the muting (block1308) including refraining from configuring any access terminals fortransmission during the last symbol period of the last uplink subframe.As an example, the one or more symbol periods may be designated fortransmission of an SRS. The access point may broadcast an indication ofan SRS gap during the one or more symbol periods.

As further discussed above in more detail, the one or more symbolperiods may include, for example, a first symbol period of a firstdownlink subframe in the third portion of the series of subframes, withthe muting (block 1308) including refraining from transmitting by anaccess point during the first symbol period of the first downlinksubframe. As an example, the one or more symbol periods may bedesignated for transmission of a PDCCH. Here, the access point may sendcontrol signaling designated for the PDCCH via another channel oranother carrier (than that of the PDCCH).

As also discussed above, a channel reservation message may betransmitted to reserve the communication medium for the series ofsubframes.

FIG. 14 is a flow diagram illustrating another example method ofcommunication in accordance with the techniques described above. Themethod 1400 may be performed, for example, by an access point (e.g., theaccess point 110 illustrated in FIG. 1) operating on a sharedcommunication medium. As an example, the communication medium mayinclude one or more time, frequency, or space resources on an unlicensedradio frequency band shared between LTE technology and Wi-Fi technologydevices.

As shown, the access point may contend for access to a communicationmedium for a series of subframes associated with a TDD frame structure(block 1402). The access point may then transmit on the communicationmedium during a first portion of the series of subframes (block 1404).The access point may, however, refrain from transmitting on thecommunication medium during a second portion of the series of subframes(block 1406).

At some point, the access point may configure a timing advance of thesecond portion of the series of subframes to create a re-contention gapbetween the second portion of the series of subframes and a thirdportion of the series of subframes (block 1408). It will be appreciatedthat this operation may be performed at various times in relation to theother operations illustrated in FIG. 14, and that the listing ofoperations in FIG. 14 is not meant to convey a required or preferredordering.

The access point may subsequently re-contend, during the re-contentiongap, for access to the communication medium for the third portion of theseries of subframes (block 1410). The access point may then transmit onthe communication medium during the third portion of the series ofsubframes (block 1412).

As discussed in more detail above, the configuring (block 1408) mayinclude, for example, sending a timing advance command to an accessterminal instructing the access terminal to commence uplink transmissionprior to a scheduled start time of an uplink subframe of the secondportion of the series of subframes. The timing advance command mayfurther instruct the access terminal to shorten a subframe of the firstportion of the series of subframes, such as a special subframe precedingthe uplink subframe. Here, the special subframe may be shortened by oneor more symbol periods as compared to the uplink subframe. As anexample, the special subframe may be shortened by between one and threesymbol periods as compared to the uplink subframe.

In some designs, a first channel reservation message may be transmittedto reserve the communication medium for the series of subframes. Asecond channel reservation message may also be transmitted to furtherreserve the communication medium for the third portion of the series ofsubframes.

For generality, the access point 110 and the access terminal 120 areshown in FIG. 1 only in relevant part as including the medium accessmanager 112 and the medium access manager 122, respectively. It will beappreciated, however, that the access point 110 and the access terminal120 may be configured in various ways to provide or otherwise supportthe re-contention techniques discussed herein.

FIG. 15 is a device-level diagram illustrating example components of theaccess point 110 and the access terminal 120 of the primary RAT system100 in more detail. As shown, the access point 110 and the accessterminal 120 may each generally include a wireless communication device(represented by the communication devices 1530 and 1550) forcommunicating with other wireless nodes via at least one designated RAT.The communication devices 1530 and 1550 may be variously configured fortransmitting and encoding signals, and, conversely, for receiving anddecoding signals in accordance with the designated RAT (e.g., messages,indications, information, pilots, and so on).

The communication devices 1530 and 1550 may include, for example, one ormore transceivers, such as respective primary RAT transceivers 1532 and1552, and, in some designs, (optional) co-located secondary RATtransceivers 1534 and 1554, respectively (corresponding, for example, tothe RAT employed by the competing RAT system 150). As used herein, a“transceiver” may include a transmitter circuit, a receiver circuit, ora combination thereof, but need not provide both transmit and receivefunctionalities in all designs. For example, a low functionalityreceiver circuit may be employed in some designs to reduce costs whenproviding full communication is not necessary (e.g., a radio chip orsimilar circuitry providing low-level sniffing only). Further, as usedherein, the term “co-located” (e.g., radios, access points,transceivers, etc.) may refer to one of various arrangements. Forexample, components that are in the same housing; components that arehosted by the same processor; components that are within a defineddistance of one another; and/or components that are connected via aninterface (e.g., an Ethernet switch) where the interface meets thelatency requirements of any required inter-component communication(e.g., messaging).

The access point 110 and the access terminal 120 may also each generallyinclude a communication controller (represented by the communicationcontrollers 1540 and 1560) for controlling operation of their respectivecommunication devices 1530 and 1550 (e.g., directing, modifying,enabling, disabling, etc.). The communication controllers 1540 and 1560may include one or more processors 1542 and 1562, and one or morememories 1544 and 1564 coupled to the processors 1542 and 1562,respectively. The memories 1544 and 1564 may be configured to storedata, instructions, or a combination thereof, either as on-board cachememory, as separate components, a combination, etc. The processors 1542and 1562 and the memories 1544 and 1564 may be standalone communicationcomponents or may be part of the respective host system functionality ofthe access point 110 and the access terminal 120.

It will be appreciated that the medium access manager 112 and the mediumaccess manager 122 may be implemented in different ways. In somedesigns, some or all of the functionality associated therewith may beimplemented by or otherwise at the direction of at least one processor(e.g., one or more of the processors 1542 and/or one or more of theprocessors 1562) and at least one memory (e.g., one or more of thememories 1544 and/or one or more of the memories 1564). In otherdesigns, some or all of the functionality associated therewith may beimplemented as a series of interrelated functional modules.

FIG. 16 illustrates an example apparatus for implementing the mediumaccess manager 112 represented as a series of interrelated functionalmodules. In the illustrated example, the apparatus 1600 includes amodule for contending 1602, a module for transmitting 1604, a module forrefraining from transmitting 1606, a module for adjusting 1608, a modulere-contending 1610, and a module for transmitting 1612.

The module for contending 1602 may be configured to contend for accessto a communication medium for a series of subframes associated with aTDD frame structure. The module for transmitting 1604 may be configuredto transmit on the communication medium during a first portion of theseries of subframes. The module for refraining from transmitting 1606may be configured to refrain from transmitting on the communicationmedium during a second portion of the series of subframes.

The module for adjusting 1208 may be configured to adjust one or moreuplink transmission parameters associated with a triggering conditionfor invoking a contention timer. The module for re-contending 1610 maybe configured to re-contend for access to the communication medium for athird portion of the series of subframes based on the contention timer.The module for transmitting 1612 may be configured to transmit on thecommunication medium during the third portion of the series ofsubframes.

FIG. 17 illustrates an example apparatus for implementing the mediumaccess manager 112 represented as a series of interrelated functionalmodules. In the illustrated example, the apparatus 1700 includes amodule for contending 1702, a module for transmitting 1704, a modulerefraining from transmitting 1706, a module for muting 1708, a modulefor re-contending 1710, and a module for transmitting 1712.

The module for contending 1702 may be configured to contend for accessto a communication medium for a series of subframes associated with aTDD frame structure. The module for transmitting 1704 may be configuredto transmit on the communication medium during a first portion of theseries of subframes. The module for refraining from transmitting 1706may be configured to refrain from transmitting on the communicationmedium during a second portion of the series of subframes.

The module for muting 1708 may be configured to mute transmission on thecommunication medium during one or more symbol periods designated fortransmission during the series of subframes. The module forre-contending 1710 may be configured to re-contend, during the one ormore symbol periods, for access to the communication medium for a thirdportion of the series of subframes. The module for transmitting 1712 maybe configured to transmit on the communication medium during the thirdportion of the series of subframes.

FIG. 18 illustrates an example apparatus for implementing the mediumaccess manager 112 represented as a series of interrelated functionalmodules. In the illustrated example, the apparatus 1800 includes amodule for contending 1802, a module for transmitting 1804, a module forrefraining from transmitting 1806, a module for configuring 1808, amodule for re-contending 1810, and a module for transmitting 1812.

The module for contending 1802 may be configured to contend for accessto a communication medium for a series of subframes associated with aTDD frame structure. The module for transmitting 1804 may be configuredto transmit on the communication medium during a first portion of theseries of subframes. The module for refraining from transmitting 1806may be configured to refrain from transmitting on the communicationmedium during a second portion of the series of subframes.

The module for configuring 1808 may be configured to configure a timingadvance of the second portion of the series of subframes to create are-contention gap between the second portion of the series of subframesand a third portion of the series of subframes. The module forre-contending 1810 may be configured to re-contend, during there-contention gap, for access to the communication medium for the thirdportion of the series of subframes. The module for transmitting 1812 maybe configured to transmit on the communication medium during the thirdportion of the series of subframes.

The functionality of the modules of FIGS. 16-18 may be implemented invarious ways consistent with the teachings herein. In some designs, thefunctionality of these modules may be implemented as one or moreelectrical components. In some designs, the functionality of theseblocks may be implemented as a processing system including one or moreprocessor components. In some designs, the functionality of thesemodules may be implemented using, for example, at least a portion of oneor more integrated circuits (e.g., an ASIC). As discussed herein, anintegrated circuit may include a processor, software, other relatedcomponents, or some combination thereof. Thus, the functionality ofdifferent modules may be implemented, for example, as different subsetsof an integrated circuit, as different subsets of a set of softwaremodules, or a combination thereof. Also, it will be appreciated that agiven subset (e.g., of an integrated circuit and/or of a set of softwaremodules) may provide at least a portion of the functionality for morethan one module.

In addition, the components and functions represented by FIGS. 16-18, aswell as other components and functions described herein, may beimplemented using any suitable means. Such means also may beimplemented, at least in part, using corresponding structure as taughtherein. For example, the components described above in conjunction withthe “module for” components of FIGS. 16-18 also may correspond tosimilarly designated “means for” functionality. Thus, in some aspectsone or more of such means may be implemented using one or more ofprocessor components, integrated circuits, or other suitable structureas taught herein, including as an algorithm. One skilled in the art willrecognize in this disclosure an algorithm represented in the prosedescribed above, as well in sequences of actions that may be representedby pseudocode. For example, the components and functions represented byFIGS. 16-18 may include code for performing a LOAD operation, a COMPAREoperation, a RETURN operation, an IF-THEN-ELSE loop, and so on.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements. In addition, terminologyof the form “at least one of A, B, or C” or “one or more of A, B, or C”or “at least one of the group consisting of A, B, and C” used in thedescription or the claims means “A or B or C or any combination of theseelements.” For example, this terminology may include A, or B, or C, or Aand B, or A and C, or A and B and C, or 2A, or 2B, or 2C, and so on.

In view of the descriptions and explanations above, one skilled in theart will appreciate that the various illustrative logical blocks,modules, circuits, and algorithm steps described in connection with theaspects disclosed herein may be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

Accordingly, it will be appreciated, for example, that an apparatus orany component of an apparatus may be configured to (or made operable toor adapted to) provide functionality as taught herein. This may beachieved, for example: by manufacturing (e.g., fabricating) theapparatus or component so that it will provide the functionality; byprogramming the apparatus or component so that it will provide thefunctionality; or through the use of some other suitable implementationtechnique. As one example, an integrated circuit may be fabricated toprovide the requisite functionality. As another example, an integratedcircuit may be fabricated to support the requisite functionality andthen configured (e.g., via programming) to provide the requisitefunctionality. As yet another example, a processor circuit may executecode to provide the requisite functionality.

Moreover, the methods, sequences, and/or algorithms described inconnection with the aspects disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module may reside in Random-AccessMemory (RAM), flash memory, Read-only Memory (ROM), ErasableProgrammable Read-only Memory (EPROM), Electrically ErasableProgrammable Read-only Memory (EEPROM), registers, hard disk, aremovable disk, a CD-ROM, or any other form of storage medium known inthe art, transitory or non-transitory. An exemplary storage medium iscoupled to the processor such that the processor can read informationfrom, and write information to, the storage medium. In the alternative,the storage medium may be integral to the processor (e.g., cachememory).

Accordingly, it will also be appreciated, for example, that certainaspects of the disclosure can include a transitory or non-transitorycomputer-readable medium embodying a method for communication.

While the foregoing disclosure shows various illustrative aspects, itshould be noted that various changes and modifications may be made tothe illustrated examples without departing from the scope defined by theappended claims. The present disclosure is not intended to be limited tothe specifically illustrated examples alone. For example, unlessotherwise noted, the functions, steps, and/or actions of the methodclaims in accordance with the aspects of the disclosure described hereinneed not be performed in any particular order. Furthermore, althoughcertain aspects may be described or claimed in the singular, the pluralis contemplated unless limitation to the singular is explicitly stated.

What is claimed is:
 1. A communication method, comprising: contendingfor access to a communication medium for a series of subframesassociated with a Time Division Duplexing (TDD) frame structure, whereinthe contending comprises transmitting a first channel reservationmessage to reserve the communication medium for the series of subframes;transmitting on the communication medium during a first portion of theseries of subframes; configuring a timing shift of a second portion ofthe series of subframes by sending a timing shift command to commencecommunication on the communication medium earlier than scheduled for thesecond portion of the series of subframes to create a re-contention gapbetween the second portion of the series of subframes and a thirdportion of the series of subframes; re-contending, during there-contention gap, for access to the communication medium for the thirdportion of the series of subframes; and transmitting on thecommunication medium during the third portion of the series ofsubframes.
 2. The method of claim 1, wherein the timing shift command issent to an access terminal instructing the access terminal to commenceuplink transmission prior to a scheduled start time of an uplinksubframe of the second portion of the series of subframes.
 3. The methodof claim 2, wherein the timing shift command further instructs theaccess terminal to shorten a subframe of the first portion of the seriesof subframes.
 4. The method of claim 3, wherein the shortened subframeis a special subframe preceding the uplink subframe.
 5. The method ofclaim 4, wherein the special subframe is shortened by one or more symbolperiods as compared to the uplink subframe.
 6. The method of claim 5,wherein the special subframe is shortened by between one and threesymbol periods as compared to the uplink subframe.
 7. The method ofclaim 1, wherein the transmitting of the first channel reservationmessage comprises transmitting the first channel reservation messageduring a downlink subframe previous to the series of subframes.
 8. Themethod of claim 1, further comprising transmitting a second channelreservation message to further reserve the communication medium for thethird portion of the series of subframes.
 9. A communication apparatus,comprising: at least one processor; at least one memory coupled to theat least one processor, the at least one processor and the at least onememory being configured to contend for access to a communication mediumfor a series of subframes associated with a Time Division Duplexing(TDD) frame structure, wherein the contending comprises transmitting afirst channel reservation message to reserve the communication mediumfor the series of subframes; and at least one transceiver configured totransmit on the communication medium during a first portion of theseries of subframes, wherein the at least one processor and the at leastone memory are further configured to configure a timing shift of asecond portion of the series of subframes by sending a timing shiftcommand to commence communication on the communication medium earlierthan scheduled for the second portion of the series of subframes tocreate a re-contention gap between the second portion of the series ofsubframes and a third portion of the series of subframes and re-contend,during the re-contention gap, for access to the communication medium forthe third portion of the series of subframes, and wherein the at leastone transceiver is further configured to transmit on the communicationmedium during the third portion of the series of subframes.
 10. Theapparatus of claim 9, wherein the at least one transceiver is furtherconfigured to send the timing shift command to an access terminalinstructing the access terminal to commence uplink transmission prior toa scheduled start time of an uplink subframe of the second portion ofthe series of subframes.
 11. The apparatus of claim 10, wherein thetiming shift command further instructs the access terminal to shorten asubframe of the first portion of the series of subframes.
 12. Theapparatus of claim 11, wherein the shortened subframe is a specialsubframe preceding the uplink subframe.
 13. The apparatus of claim 12,wherein the special subframe is shortened by one or more symbol periodsas compared to the uplink subframe.
 14. The apparatus of claim 13,wherein the special subframe is shortened by between one and threesymbol periods as compared to the uplink subframe.
 15. The apparatus ofclaim 9, wherein the at least one transceiver is further configured totransmit the first channel reservation message during a downlinksubframe previous to the series of subframes.
 16. The apparatus of claim9, wherein the at least one transceiver is further configured totransmit a second channel reservation message to further reserve thecommunication medium for the third portion of the series of subframes.17. A communication apparatus, comprising: means for contending foraccess to a communication medium for a series of subframes associatedwith a Time Division Duplexing (TDD) frame structure, wherein thecontending comprises transmitting a first channel reservation message toreserve the communication medium for the series of subframes; means fortransmitting on the communication medium during a first portion of theseries of subframes; means for configuring a timing shift of a secondportion of the series of subframes by sending a timing shift command tocommence communication on the communication medium earlier thanscheduled for the second portion of the series of subframes to create are-contention gap between the second portion of the series of subframesand a third portion of the series of subframes; means for re-contending,during the re-contention gap, for access to the communication medium forthe third portion of the series of subframes; and means for transmittingon the communication medium during the third portion of the series ofsubframes.
 18. The apparatus of claim 17, wherein the means forconfiguring comprises means for sending the timing shift command to anaccess terminal instructing the access terminal to commence uplinktransmission prior to a scheduled start time of an uplink subframe ofthe second portion of the series of subframes.
 19. The apparatus ofclaim 18, wherein the timing shift command further instructs the accessterminal to shorten a subframe of the first portion of the series ofsubframes.
 20. The apparatus of claim 19, wherein the shortened subframeis a special subframe preceding the uplink subframe.
 21. The apparatusof claim 20, wherein the special subframe is shortened by one or moresymbol periods as compared to the uplink subframe.
 22. The apparatus ofclaim 21, wherein the special subframe is shortened by between one andthree symbol periods as compared to the uplink subframe.
 23. Theapparatus of claim 17, further comprising: means for transmitting asecond channel reservation message to further reserve the communicationmedium for the third portion of the series of subframes.
 24. Anon-transitory computer-readable medium comprising code, which, whenexecuted by a processor, causes the processor to perform operations forcommunication, the non-transitory computer-readable medium comprising:code for contending for access to a communication medium for a series ofsubframes associated with a Time Division Duplexing (TDD) framestructure, wherein the contending comprises transmitting a first channelreservation message to reserve the communication medium for the seriesof subframes; code for transmitting on the communication medium during afirst portion of the series of subframes; code for configuring a timingshift of a second portion of the series of subframes by sending a timingshift command to commence communication on the communication mediumearlier than scheduled for the second portion of the series of subframesto create a re-contention gap between the second portion of the seriesof subframes and a third portion of the series of subframes; code forre-contending, during the re-contention gap, for access to thecommunication medium for the third portion of the series of subframes;and code for transmitting on the communication medium during the thirdportion of the series of subframes.
 25. The non-transitorycomputer-readable medium of claim 24, wherein the code for configuringcomprises code for sending the timing shift command to an accessterminal instructing the access terminal to commence uplink transmissionprior to a scheduled start time of an uplink subframe of the secondportion of the series of subframes.
 26. The non-transitorycomputer-readable medium of claim 25, wherein the timing shift commandfurther instructs the access terminal to shorten a subframe of the firstportion of the series of subframes.
 27. The non-transitorycomputer-readable medium of claim 26, wherein the shortened subframe isa special subframe preceding the uplink subframe.
 28. The non-transitorycomputer-readable medium of claim 27, wherein the special subframe isshortened by one or more symbol periods as compared to the uplinksubframe.
 29. The non-transitory computer-readable medium of claim 28,wherein the special subframe is shortened by between one and threesymbol periods as compared to the uplink subframe.
 30. Thenon-transitory computer-readable medium of claim 24, further comprising:code for transmitting a second channel reservation message to furtherreserve the communication medium for the third portion of the series ofsubframes.